Internal combustion engines, for example, diesel engines, gasoline engines, or natural gas engines employ turbochargers to deliver compressed air for combustion in the engine. A turbocharger compresses air flowing into the engine, helping to force more air into combustion chambers of the engine. The increased supply of air allows for increased fuel combustion in the combustion chambers, resulting in increased power output from the engine.
A typical turbocharger includes a shaft, a turbine wheel connected to one end of the shaft, a compressor wheel connected to the other end of the shaft, and bearings to support the shaft. Separate housings connected to each other enclose the compressor wheel, the turbine wheel, and the bearings. Exhaust from the engine expands over the turbine wheel and rotates the turbine wheel. The turbine wheel in turn rotates the compressor wheel via the shaft. The compressor wheel receives cool air from the ambient and forces compressed air into combustion chambers of the engine.
The compressor stage of a turbocharger often includes a diffuser configured to reduce the speed of the air leaving the compressor wheel. Reducing the air speed causes the air pressure within the compressor stage to increase, which in turn helps to deliver compressed air to the combustion chambers of the engine. The compressor diffuser usually includes vanes extending between the bearing housing and the compressor housing. These vanes direct the spinning air from the compressor impeller into the compressor housing volute. Air flowing around the vanes in the diffuser creates pressure wakes as the air stream separates to flow around the vanes in the diffuser. The pressure wakes in turn may induce high frequency vibrations in the compressor impeller blades, which in turn may cause fatigue failure of the compressor impeller blades.
U.S. Pat. No. 4,302,150 of Wieland that issued on Nov. 24, 1981 (“the '150 patent”) discloses a centrifugal compressor with a diffuser and a vaneless diffuser space. In particular, the '150 patent discloses a radial flow compressor having a diffuser ring disposed radially outward from the outer edges of the compressor impeller blades. The '150 patent discloses that the radial tips of the impeller blades and the diffuser ring define a vaneless diffuser space. The '150 patent further discloses that the vaneless diffuser space circumferentially surrounds the impeller. The '150 patent also discloses that the vaneless diffuser space, by virtue of its lack of vanes or other structural barriers, serves to smooth out wake and sonic shock effects inherent in the compressed fluid discharged radially outwardly from the impeller blades.
Although the '150 patent discloses a vaneless diffuser space, the disclosed vaneless diffuser space may still not be optimal. For example, although the disclosed vaneless diffuser space may smooth out the wake effects generated by the compressor impeller blades, the vaneless diffuser space may not be large enough to prevent high frequency excitation of the compressor impeller blades caused by the wakes generated at the diffuser vanes. Furthermore, the disclosed vaneless diffuser space may not be suitable for mixed flow compressors where the flow leaving the compressor impeller blades may not be radial but may include angular and axial velocity components.
The compressor assembly of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.